Shrinking!!!!

In the last 3 years I've shrank 3 inches. I just turned 21 in June and have no idea why this is happening!? Has anyone else experienced this or have any insight on what I should do to prevent anymore shrinkage to happen?? No one in my family going back to my great grandma has shrank more than 1/2. I'm kind of worried, will this effect my chances on conceiving??